A pinch of Physics is required!

Classical Mechanics Level 2

You have a piece of aluminium whose mass is 800 g 800\text{ g} , and suppose it is heated up to 100 0 ∘ C . 1000^\circ\text{C}.

Now, given that you are cooling it down to 15 0 ∘ C 150^\circ\text{C} , calculate the amount of heat (in Joules) given out during the process of cooling.

Details and assumptions:

  • The specific heat capacity of aluminium is C Aluminum = 900 J / kg K . \text{C}_\text{Aluminum}=900 \text{ J}/\text{kg K}.
  • Ignore the heat energy lost to the atmosphere.
Image credit : hardy solutions


The answer is 612000.

Sravanth C. by Sravanth C. , 21, India

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2 solutions

Sravanth C.
May 19, 2015

The following values are given,

m a s s = 800 g = 0.8 k g I n i t i a l t e m p e r a t u r e = T 1 = 1000 ° C = 1273 ° K F i n a l t e m p e r a t u r e = 150 ° C = 423 ° K C a l u m i n i u m = 900 J / k g K mass=800g=0.8kg \\ Initial \quad temperature=T_{1}=1000°C=1273°K \\ Final \quad temperature =150°C=423°K \\ C_{aluminium}=900J/kgK

We know that heat energy Q Q is given by the following expression,

Q = C m Δ T = 900 × 0.8 × ( 1273 − 423 ) = 720 × 850 = 612000 J Q=Cm\Delta T \\ =900×0.8×(1273-423) \\ =720×850 \\ =612000J

6 Helpful 0 Interesting 1 Brilliant 0 Confused

I think you meant Δ T \Delta T .BTW

C h e e r s ! \huge Cheers!

Nihar Mahajan - 6 years ago

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Thanks! Edited.

Sravanth C. - 6 years ago
Nihar Mahajan
May 19, 2015

My solution is almost similar to that of Sravanth but I like celsius more than kelvin.

C a l u m i n i u m = 900 J / k g K = 900 J / k g C C_{aluminium}=900J/kg K =900J/kg C \ because a unit change in celsius is equal to unit change in kelvin.So the formula for release of heat is given by :

Δ Q = m . C a l u m i n i u m Δ T = ( 0.8 ) ( 900 ) ( 1000 − 150 ) = 612000 J \Delta Q = m.C_{aluminium} \Delta T = (0.8)(900)(1000-150)=612000 J

5 Helpful 0 Interesting 0 Brilliant 0 Confused

Oh yeah! The change in temperatures in both the scales is the same.

C H E E R S ! ! ! \huge CHEERS!!!

Sravanth C. - 6 years ago

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⌣ ¨ ⌣ ¨ ⌣ ¨ \ddot\smile\ddot\smile\ddot\smile

Nihar Mahajan - 6 years ago

Have some room for me back there guys? xD

Arian Tashakkor - 6 years ago

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